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<FONT color="green">001</FONT>    /*<a name="line.1"></a>
<FONT color="green">002</FONT>     * Copyright Aduna (http://www.aduna-software.com/) (c) 2008-2009.<a name="line.2"></a>
<FONT color="green">003</FONT>     *<a name="line.3"></a>
<FONT color="green">004</FONT>     * Licensed under the Aduna BSD-style license.<a name="line.4"></a>
<FONT color="green">005</FONT>     */<a name="line.5"></a>
<FONT color="green">006</FONT>    package com.fluidops.fedx.evaluation.iterator;<a name="line.6"></a>
<FONT color="green">007</FONT>    <a name="line.7"></a>
<FONT color="green">008</FONT>    <a name="line.8"></a>
<FONT color="green">009</FONT>    <a name="line.9"></a>
<FONT color="green">010</FONT>    import info.aduna.iteration.LookAheadIteration;<a name="line.10"></a>
<FONT color="green">011</FONT>    <a name="line.11"></a>
<FONT color="green">012</FONT>    import java.util.ArrayList;<a name="line.12"></a>
<FONT color="green">013</FONT>    import java.util.Arrays;<a name="line.13"></a>
<FONT color="green">014</FONT>    import java.util.LinkedList;<a name="line.14"></a>
<FONT color="green">015</FONT>    import java.util.List;<a name="line.15"></a>
<FONT color="green">016</FONT>    import java.util.Queue;<a name="line.16"></a>
<FONT color="green">017</FONT>    import java.util.concurrent.ArrayBlockingQueue;<a name="line.17"></a>
<FONT color="green">018</FONT>    import java.util.concurrent.BlockingQueue;<a name="line.18"></a>
<FONT color="green">019</FONT>    <a name="line.19"></a>
<FONT color="green">020</FONT>    import org.openrdf.query.QueryEvaluationException;<a name="line.20"></a>
<FONT color="green">021</FONT>    <a name="line.21"></a>
<FONT color="green">022</FONT>    /**<a name="line.22"></a>
<FONT color="green">023</FONT>     * Makes working with a queue easier by adding the methods {@link #done()} and<a name="line.23"></a>
<FONT color="green">024</FONT>     * {@link #toss(Exception)} and automatically converting the exception into a<a name="line.24"></a>
<FONT color="green">025</FONT>     * QueryEvaluationException with an appropriate stack trace.<a name="line.25"></a>
<FONT color="green">026</FONT>     * <a name="line.26"></a>
<FONT color="green">027</FONT>     * @author James Leigh<a name="line.27"></a>
<FONT color="green">028</FONT>     */<a name="line.28"></a>
<FONT color="green">029</FONT>    public class QueueCursor&lt;E&gt; extends LookAheadIteration&lt;E, QueryEvaluationException&gt; {<a name="line.29"></a>
<FONT color="green">030</FONT>    <a name="line.30"></a>
<FONT color="green">031</FONT>            private volatile boolean done;<a name="line.31"></a>
<FONT color="green">032</FONT>    <a name="line.32"></a>
<FONT color="green">033</FONT>            private BlockingQueue&lt;E&gt; queue;<a name="line.33"></a>
<FONT color="green">034</FONT>    <a name="line.34"></a>
<FONT color="green">035</FONT>            private E afterLast = createAfterLast();<a name="line.35"></a>
<FONT color="green">036</FONT>    <a name="line.36"></a>
<FONT color="green">037</FONT>            private volatile Queue&lt;Throwable&gt; exceptions = new LinkedList&lt;Throwable&gt;();<a name="line.37"></a>
<FONT color="green">038</FONT>    <a name="line.38"></a>
<FONT color="green">039</FONT>            /**<a name="line.39"></a>
<FONT color="green">040</FONT>             * Creates an &lt;tt&gt;QueueCursor&lt;/tt&gt; with the given (fixed) capacity and<a name="line.40"></a>
<FONT color="green">041</FONT>             * default access policy.<a name="line.41"></a>
<FONT color="green">042</FONT>             * <a name="line.42"></a>
<FONT color="green">043</FONT>             * @param capacity<a name="line.43"></a>
<FONT color="green">044</FONT>             *        the capacity of this queue<a name="line.44"></a>
<FONT color="green">045</FONT>             */<a name="line.45"></a>
<FONT color="green">046</FONT>            public QueueCursor(int capacity) {<a name="line.46"></a>
<FONT color="green">047</FONT>                    this(capacity, false);<a name="line.47"></a>
<FONT color="green">048</FONT>            }<a name="line.48"></a>
<FONT color="green">049</FONT>    <a name="line.49"></a>
<FONT color="green">050</FONT>            /**<a name="line.50"></a>
<FONT color="green">051</FONT>             * Creates an &lt;tt&gt;QueueCursor&lt;/tt&gt; with the given (fixed) capacity and the<a name="line.51"></a>
<FONT color="green">052</FONT>             * specified access policy.<a name="line.52"></a>
<FONT color="green">053</FONT>             * <a name="line.53"></a>
<FONT color="green">054</FONT>             * @param capacity<a name="line.54"></a>
<FONT color="green">055</FONT>             *        the capacity of this queue<a name="line.55"></a>
<FONT color="green">056</FONT>             * @param fair<a name="line.56"></a>
<FONT color="green">057</FONT>             *        if &lt;tt&gt;true&lt;/tt&gt; then queue accesses for threads blocked on<a name="line.57"></a>
<FONT color="green">058</FONT>             *        insertion or removal, are processed in FIFO order; if<a name="line.58"></a>
<FONT color="green">059</FONT>             *        &lt;tt&gt;false&lt;/tt&gt; the access order is unspecified.<a name="line.59"></a>
<FONT color="green">060</FONT>             */<a name="line.60"></a>
<FONT color="green">061</FONT>            public QueueCursor(int capacity, boolean fair) {<a name="line.61"></a>
<FONT color="green">062</FONT>                    this.queue = new ArrayBlockingQueue&lt;E&gt;(capacity, fair);<a name="line.62"></a>
<FONT color="green">063</FONT>            }<a name="line.63"></a>
<FONT color="green">064</FONT>    <a name="line.64"></a>
<FONT color="green">065</FONT>            /**<a name="line.65"></a>
<FONT color="green">066</FONT>             * The next time {@link #next()} is called this exception will be thrown. If<a name="line.66"></a>
<FONT color="green">067</FONT>             * it is not a QueryEvaluationException or RuntimeException it will be wrapped in a<a name="line.67"></a>
<FONT color="green">068</FONT>             * QueryEvaluationException.<a name="line.68"></a>
<FONT color="green">069</FONT>             */<a name="line.69"></a>
<FONT color="green">070</FONT>            public void toss(Exception exception) {<a name="line.70"></a>
<FONT color="green">071</FONT>                    synchronized (exceptions) {<a name="line.71"></a>
<FONT color="green">072</FONT>                            exceptions.add(exception);<a name="line.72"></a>
<FONT color="green">073</FONT>                    }<a name="line.73"></a>
<FONT color="green">074</FONT>            }<a name="line.74"></a>
<FONT color="green">075</FONT>    <a name="line.75"></a>
<FONT color="green">076</FONT>            /**<a name="line.76"></a>
<FONT color="green">077</FONT>             * Adds another item to the queue, blocking while the queue is full.<a name="line.77"></a>
<FONT color="green">078</FONT>             */<a name="line.78"></a>
<FONT color="green">079</FONT>            public void put(E st)<a name="line.79"></a>
<FONT color="green">080</FONT>                    throws InterruptedException<a name="line.80"></a>
<FONT color="green">081</FONT>            {<a name="line.81"></a>
<FONT color="green">082</FONT>                    queue.put(st);<a name="line.82"></a>
<FONT color="green">083</FONT>            }<a name="line.83"></a>
<FONT color="green">084</FONT>    <a name="line.84"></a>
<FONT color="green">085</FONT>            /**<a name="line.85"></a>
<FONT color="green">086</FONT>             * Indicates the method {@link #put(Object)} will not be called in the queue<a name="line.86"></a>
<FONT color="green">087</FONT>             * anymore.<a name="line.87"></a>
<FONT color="green">088</FONT>             */<a name="line.88"></a>
<FONT color="green">089</FONT>            public void done() {<a name="line.89"></a>
<FONT color="green">090</FONT>                    done = true;<a name="line.90"></a>
<FONT color="green">091</FONT>                    try {<a name="line.91"></a>
<FONT color="green">092</FONT>                            queue.add(afterLast);<a name="line.92"></a>
<FONT color="green">093</FONT>                    }<a name="line.93"></a>
<FONT color="green">094</FONT>                    catch (IllegalStateException e) {<a name="line.94"></a>
<FONT color="green">095</FONT>                            // no thread is waiting on this queue anyway<a name="line.95"></a>
<FONT color="green">096</FONT>                    }<a name="line.96"></a>
<FONT color="green">097</FONT>            }<a name="line.97"></a>
<FONT color="green">098</FONT>    <a name="line.98"></a>
<FONT color="green">099</FONT>            /**<a name="line.99"></a>
<FONT color="green">100</FONT>             * Returns the next item in the queue or throws an exception.<a name="line.100"></a>
<FONT color="green">101</FONT>             */<a name="line.101"></a>
<FONT color="green">102</FONT>            @Override<a name="line.102"></a>
<FONT color="green">103</FONT>            public E getNextElement()<a name="line.103"></a>
<FONT color="green">104</FONT>                    throws QueryEvaluationException<a name="line.104"></a>
<FONT color="green">105</FONT>            {<a name="line.105"></a>
<FONT color="green">106</FONT>                    try {<a name="line.106"></a>
<FONT color="green">107</FONT>                            checkException();<a name="line.107"></a>
<FONT color="green">108</FONT>                            E take;<a name="line.108"></a>
<FONT color="green">109</FONT>                            if (done) {<a name="line.109"></a>
<FONT color="green">110</FONT>                                    take = queue.poll();<a name="line.110"></a>
<FONT color="green">111</FONT>                            }<a name="line.111"></a>
<FONT color="green">112</FONT>                            else {<a name="line.112"></a>
<FONT color="green">113</FONT>                                    take = queue.take();<a name="line.113"></a>
<FONT color="green">114</FONT>                                    if (done) {<a name="line.114"></a>
<FONT color="green">115</FONT>                                            done(); // in case the queue was full before<a name="line.115"></a>
<FONT color="green">116</FONT>                                    }<a name="line.116"></a>
<FONT color="green">117</FONT>                            }<a name="line.117"></a>
<FONT color="green">118</FONT>                            if (isAfterLast(take)) {<a name="line.118"></a>
<FONT color="green">119</FONT>                                    checkException();<a name="line.119"></a>
<FONT color="green">120</FONT>                                    done(); // put afterLast back for others<a name="line.120"></a>
<FONT color="green">121</FONT>                                    return null;<a name="line.121"></a>
<FONT color="green">122</FONT>                            }<a name="line.122"></a>
<FONT color="green">123</FONT>                            return take;<a name="line.123"></a>
<FONT color="green">124</FONT>                    }<a name="line.124"></a>
<FONT color="green">125</FONT>                    catch (InterruptedException e) {<a name="line.125"></a>
<FONT color="green">126</FONT>                            checkException();<a name="line.126"></a>
<FONT color="green">127</FONT>                            throw new QueryEvaluationException(e);<a name="line.127"></a>
<FONT color="green">128</FONT>                    }<a name="line.128"></a>
<FONT color="green">129</FONT>            }<a name="line.129"></a>
<FONT color="green">130</FONT>    <a name="line.130"></a>
<FONT color="green">131</FONT>            @Override<a name="line.131"></a>
<FONT color="green">132</FONT>            public void handleClose()<a name="line.132"></a>
<FONT color="green">133</FONT>                    throws QueryEvaluationException<a name="line.133"></a>
<FONT color="green">134</FONT>            {<a name="line.134"></a>
<FONT color="green">135</FONT>                    checkException();<a name="line.135"></a>
<FONT color="green">136</FONT>            }<a name="line.136"></a>
<FONT color="green">137</FONT>            public void checkException()<a name="line.137"></a>
<FONT color="green">138</FONT>                    throws QueryEvaluationException<a name="line.138"></a>
<FONT color="green">139</FONT>            {<a name="line.139"></a>
<FONT color="green">140</FONT>                    synchronized (exceptions) {<a name="line.140"></a>
<FONT color="green">141</FONT>                            if (!exceptions.isEmpty()) {<a name="line.141"></a>
<FONT color="green">142</FONT>                                    try {<a name="line.142"></a>
<FONT color="green">143</FONT>                                            throw exceptions.remove();<a name="line.143"></a>
<FONT color="green">144</FONT>                                    }<a name="line.144"></a>
<FONT color="green">145</FONT>                                    catch (QueryEvaluationException e) {<a name="line.145"></a>
<FONT color="green">146</FONT>                                            List&lt;StackTraceElement&gt; stack = new ArrayList&lt;StackTraceElement&gt;();<a name="line.146"></a>
<FONT color="green">147</FONT>                                            stack.addAll(Arrays.asList(e.getStackTrace()));<a name="line.147"></a>
<FONT color="green">148</FONT>                                            StackTraceElement[] thisStack = new Throwable().getStackTrace();<a name="line.148"></a>
<FONT color="green">149</FONT>                                            stack.addAll(Arrays.asList(thisStack).subList(1, thisStack.length));<a name="line.149"></a>
<FONT color="green">150</FONT>                                            e.setStackTrace(stack.toArray(new StackTraceElement[stack.size()]));<a name="line.150"></a>
<FONT color="green">151</FONT>                                            throw e;<a name="line.151"></a>
<FONT color="green">152</FONT>                                    }<a name="line.152"></a>
<FONT color="green">153</FONT>                                    catch (RuntimeException e) {<a name="line.153"></a>
<FONT color="green">154</FONT>                                            List&lt;StackTraceElement&gt; stack = new ArrayList&lt;StackTraceElement&gt;();<a name="line.154"></a>
<FONT color="green">155</FONT>                                            stack.addAll(Arrays.asList(e.getStackTrace()));<a name="line.155"></a>
<FONT color="green">156</FONT>                                            StackTraceElement[] thisStack = new Throwable().getStackTrace();<a name="line.156"></a>
<FONT color="green">157</FONT>                                            stack.addAll(Arrays.asList(thisStack));<a name="line.157"></a>
<FONT color="green">158</FONT>                                            e.setStackTrace(stack.toArray(new StackTraceElement[stack.size()]));<a name="line.158"></a>
<FONT color="green">159</FONT>                                            throw e;<a name="line.159"></a>
<FONT color="green">160</FONT>                                    }<a name="line.160"></a>
<FONT color="green">161</FONT>                                    catch (Throwable e) {<a name="line.161"></a>
<FONT color="green">162</FONT>                                            throw new QueryEvaluationException(e);<a name="line.162"></a>
<FONT color="green">163</FONT>                                    }<a name="line.163"></a>
<FONT color="green">164</FONT>                            }<a name="line.164"></a>
<FONT color="green">165</FONT>                    }<a name="line.165"></a>
<FONT color="green">166</FONT>            }<a name="line.166"></a>
<FONT color="green">167</FONT>    <a name="line.167"></a>
<FONT color="green">168</FONT>            private boolean isAfterLast(E take) {<a name="line.168"></a>
<FONT color="green">169</FONT>                    return take == null || take == afterLast;<a name="line.169"></a>
<FONT color="green">170</FONT>            }<a name="line.170"></a>
<FONT color="green">171</FONT>    <a name="line.171"></a>
<FONT color="green">172</FONT>            @SuppressWarnings("unchecked")<a name="line.172"></a>
<FONT color="green">173</FONT>            private E createAfterLast() {<a name="line.173"></a>
<FONT color="green">174</FONT>                    return (E)new Object();<a name="line.174"></a>
<FONT color="green">175</FONT>            }<a name="line.175"></a>
<FONT color="green">176</FONT>    <a name="line.176"></a>
<FONT color="green">177</FONT>    }<a name="line.177"></a>




























































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